Catadioptric lithography system and method with reticle stage orthogonal to wafer stage

ABSTRACT

The present invention relates to a lithography apparatus using catadioptric exposure optics that projects high quality images without image flip. The lithography apparatus includes a reticle stage, a wafer stage, and a catadioptric exposure optics located between the reticle stage and the wafer stage. The catadioptric exposure optics projects an image from the reticle stage onto the wafer stage. The projected image has the same image orientation as the image from the reticle stage. In other words, the catadioptric exposure optics does not perform image flip. The reticle stage lies on a first plane and the wafer stage lies on a second plane, where the first plane is orthogonal to the second plane. In another embodiment of the present invention, the catadioptric exposure optics projects an even number of reflections. The projected image is of high precision and lacks aberrations such as perspective warping and obscured areas. The invention can be combined with a dual wafer stage and with a dual isolation system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is related to the following commonly-owned U.S.Patent Applications: U.S. patent application Ser. No. 09/449,630, nowabandoned to Roux et al, entitled “Dual Stage Lithography Apparatus andMethod,” filed Nov. 30, 1999 and U.S. Pat. No. 6,538,720, to Galburt etal, for “Lithographic Tool with Dual Isolation System and Method forConfiguring the Same,” issued Mar. 25, 2003. The foregoing U.S. PatentApplications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved lithography system and method.More specifically, this invention relates to a lithography system andmethod using catadioptric exposure optics that projects high precisionimages without image flip.

2. Background Art

Lithography is a process used to create features on the surface ofsubstrates. Such substrates can include those used in the manufacture offlat panel displays, circuit boards, various integrated circuits, andthe like. A frequently used substrate for such applications is asemiconductor wafer. While this description is written in terms of asemiconductor wafer for illustrative purposes, one skilled in the artwould recognize that this description also applies to other types ofsubstrates known to those skilled in the art. During lithography, awafer, which is disposed on a wafer stage, is exposed to an imageprojected onto the surface of the wafer by exposure optics locatedwithin a lithography apparatus. The image refers to the original, orsource, image being exposed. The projected image refers to the imagewhich actually contacts the surface of the wafer. While exposure opticsare used in the case of photolithography, a different type of exposureapparatus may be used depending on the particular application. Forexample, x-ray or photon lithographies each may require a differentexposure apparatus, as is known to those skilled in the art. Theparticular example of photolithography is discussed here forillustrative purposes only.

The projected image produces changes in the characteristics of a layer,for example photoresist, deposited on the surface of the wafer. Thesechanges correspond to the features projected onto the wafer duringexposure. Subsequent to exposure, the layer can be etched to produce apatterned layer. The pattern corresponds to those features projectedonto the wafer during exposure. This patterned layer is then used toremove exposed portions of underlying structural layers within thewafer, such as conductive, semiconductive, or insulative layers. Thisprocess is then repeated, together with other steps, until the desiredfeatures have been formed on the surface of the wafer.

Exposure optics comprise refractive and/or reflective elements, i.e.,lenses and/or mirrors. Currently, most exposure optics used forcommercial manufacturing consist only of lenses. However, the use ofcatadioptric (i.e., a combination of refractive and reflective elements)exposure optics is increasing. The use of refractive and reflectiveelements allows for a greater number of lithographic variables to becontrolled during manufacturing. The use of mirrors, however, can leadto image flip problems.

Image flip occurs when an image is reflected off of a mirror. FIG. 1shows an example of image flip. In this example, if one were to hold upplain English text to a mirror, one would notice that the text, viewedin the mirror, would appear to be written backwards. Thus, an image ofthe letter “F,” would be seen as “” in the mirror. This shows that whenan image is reflected off of a mirror, the projected image results in anincorrect image orientation, i.e., the image transfer produces imageflip. Of course, if the image is reflected off of two mirrors, the imageorientation of the projected image would be correct because the image isflipped twice. Thus, an image of the letter “F,” would be seen as “F”after the second reflection. Therefore, it can be seen that image flipresults when an image is reflected an odd number of times. Conversely,it can be seen that image flip does not result when the image isreflected an even number of times.

Current lithographic systems typically include a reticle stage that isparallel to a wafer stage, such that the image from the reticle stage isprojected downward onto the wafer stage. In addition, currentlithographic systems typically include catadioptric exposure optics thatrequire a magnifying mirror, such as a concave asphere. This mirrorenhances the projected image and enables better exposure of the wafer.The parallel wafer and reticle stages together with the geometry of amagnifying mirror, however, makes it difficult for the catadioptricexposure optics to perform an even number of reflections.

To illustrate this point, FIG. 2 shows a simplified example lithographicsystem 200. System 200 shows a parallel reticle stage 202 and waferstage 204 using catadioptric exposure optics 212, having a first mirror206, a beam splitter 208, a quarter wave plate 209, and a magnifyingmirror element group 210. In this example system 200, an image isprojected from reticle stage 202 using P polarized light. This polarizedlight is reflected by first mirror 206 directly into magnifying mirrorelement group 210. It should be noted that quarter wave plate 209 canrotate the polarization angle of the light. The reflected image fromfirst mirror 206 passes through beam splitter 208. This is due to the Ppolarization of the light being transmitted by beam splitter 208. Thereflected image from magnifying mirror element group 210 has itspolarization angle rotated 90°. This light is reflected at the beamsplitter surface onto wafer 204. Thus, S polarization is not transmittedby beam splitter 208. Subsequently, the image is reflected directly outof magnifying mirror element group 210 that contains quarter wave plate209. Besides flipping the image, magnifying mirror element group 210also reverses the polarization of the image. Thus, the image reflectedout of magnifying mirror element group 210 is then reflected by beamsplitter 208, since the image now has the opposite polarization as beamsplitter 208. The image is then projected onto parallel wafer stage 204.Using this configuration, an odd number of reflections occur. As aresult, image flip problems occur.

Several alternative lithographic system designs, however, have attemptedto overcome the image flip obstacle. One such design is a centrallyobscured optical system design. FIG. 3 shows an example lithographicsystem 300 with a centrally obscured optical system design. System 300shows a parallel reticle stage 302 and wafer stage 304 usingcatadioptric exposure optics 312 with a first mirror 306 and amagnifying mirror 308. In this example system 300, an image is projectedfrom reticle stage 302 directly into magnifying mirror 308. It should benoted that the image projected from reticle stage 302 passes throughfirst mirror 306. This is because first mirror 306 is polarized (in thesame way as beam splitter 208 above). The image is then reflecteddirectly out of magnifying mirror 308 and onto first mirror 306. Besidesflipping the image, magnifying mirror 308 also reverses the polarizationof the image. The image is then reflected downwards by first mirror 306,through a small hole 310 in magnifying mirror 308 and onto wafer stage304. In this configuration, magnifying mirror 308 is in the path of theprojected reflection of first mirror 306, which is why small hole 310exists within magnifying mirror 308. The projected reflection of firstmirror 306 travels through small hole 310 in magnifying mirror 308 toreach wafer stage 304. Using this configuration, an even number ofreflections occur. Thus, there is no image flip problem. However, thisconfiguration has its drawbacks. As the image is reflected by magnifyingmirror 308, some of the image information (namely the portion of theimage that passes through small hole 310 in magnifying mirror 308) islost. This can produce aberrations or inconsistencies in the projectedimage.

Another lithographic system that has attempted to overcome the imageflip obstacle is an off-axis design. FIG. 4 shows an examplelithographic system 400 with an off-axis design. System 400 shows aparallel reticle stage 402 and wafer stage 404 using catadioptricexposure optics 412 with a first mirror 406 and a magnifying mirror 408.In this example system 400, an image is projected from reticle stage 402onto a first mirror 406, reflected from first mirror 406 and intomagnifying mirror 408, reflected out of magnifying mirror 408 and ontowafer stage 404. In this configuration, reticle stage 402 is off-axisfrom wafer stage 404. This is because the image is reflected away fromthe reticle stage in order to magnify it using magnifying mirror 408. Asshown, there is a small angle 410 between first mirror 406 and waferstage 404. Using this configuration, an even number of reflectionsoccur. However, this configuration has its drawbacks. Magnifying mirror408 does not directly (i.e., perpendicularly) receive the reflectedimage from first mirror 406. This is because magnifying mirror 408 mustbe able to receive a reflected image from first mirror 406 and reflectthat image through a small angle 410 onto wafer stage 404. Further,magnifying mirror 408 does not directly reflect the image onto waferstage 404. As a result, aberrations and perspective warping of the imagecan occur.

Therefore, it is difficult to create a lithographic system withcatadioptric exposure optics that can produce a high quality imagewithout image flip. Consequently, most lithographic systems today use adesign similar to the design of FIG. 1. This design performs anodd-number of reflections that result in image flip problems. As aresult, when exposing an image using these catadioptric exposure optics,it must be kept in mind that the projected image is the reverse of thedesired image. This can lead to increased processing time andpreparation. This problem is further compounded by the fact that mostlithographic systems used today do not result in image flip. As aresult, manufacturers that use both catadioptric exposure optics andnon-catadioptric exposure optics (i.e., systems that have the image flipproblem and systems that do not have the image flip problem) must usetwo reticle plates-one with each image orientation. This can lead tohigher production costs.

In view of the above, what is needed is a lithographic system andmethod, using catadioptric exposure optics, which produces a highprecision image without image flip.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a lithography system and method usingcatadioptric exposure optics that projects high quality images withoutimage flip.

In an embodiment of the present invention, the lithography system andmethod includes a reticle stage, a wafer stage, and a catadioptricexposure optics located between the reticle stage and the wafer stage.The catadioptric exposure optics projects an image from the reticlestage onto the wafer stage. The projected image has the same imageorientation as the image from the reticle stage. In other words, thecatadioptric exposure optics does not perform image flip.

In an embodiment of the present invention, the reticle stage lies on afirst plane and the wafer stage lies on a second plane, where the firstplane is orthogonal to the second plane. In another embodiment of thepresent invention, the catadioptric exposure optics performs an evennumber of reflections. According to the present invention, the projectedimage is of high precision. Moreover, the projected image lacksaberrations such as perspective warping and obscured areas.

In another embodiment of the present invention, two wafer stages areused. Each wafer stage has associated load/unload and data collectionstations. The load/unload and data collection stations are located oneither side of an exposure station. The wafer stages are mounted on acommon rail such that as a first stage moves away from the exposurestation, a second stage can immediately move in to take its place underthe exposure apparatus. Through this arrangement, use of the exposureapparatus is maximized. Because wafer data collection and exposure stepsoccur in parallel in the instant invention, the compromised waferalignment strategies, sometimes employed to increase throughput, neednot be used. In fact, the parallel nature of the instant inventionallows for greater data collection without a corresponding decrease inthroughput.

In another embodiment of the present invention, a dual isolation systemis used. In one aspect, an isolated base frame is supported by anon-isolated tool structure. The wafer stage components are supported bythe isolated base frame. The wafer stage components provide a mount forattachment of a semiconductor wafer. The reticle stage component issupported by the isolated base frame. The reticle stage componentprovides a mount for a reticle. An isolated bridge provides a mount forexposure optics. The isolated bridge is supported by the isolated baseframe. Radiation from an illumination source passes through a reticlemounted at the provided reticle mount to a surface of an attachedsemiconductor wafer. A pattern of a mounted reticle is transferred to asurface of an attached semiconductor wafer.

An advantage of the present invention is the use of catadioptricexposure optics that does not perform image flip. This allows amanufacturer to use the same image with catadioptric andnon-catadioptric lithographic systems. This increases compatibility andreduces production costs.

Another advantage of the present invention is projection of a highprecision image onto the wafer stage. Unlike the prior art which usesalternative catadioptric exposure optics designs, the present inventionprojects a high quality image without aberrations such as perspectivewarping and obscuration areas in the optics pupil. This produces ahigher quality product.

Another advantage of the present invention is maximization of the use ofthe exposure optics. This is due to wafer data collection and exposuresteps occurring in parallel. The parallel nature of the presentinvention allows for greater data collection without a correspondingdecrease in throughput. This increases the efficiency of themanufacturing process.

Another advantage of the present invention is the reduction of relativemotion between critical elements of the lithography apparatus. Thepresent invention uses multiple isolated systems to reduce motion loads,and relative motion between critical components, including componentssuch as those included in a wafer stage, a reticle stage, and exposureoptics. By reducing motion loads, and relative motion between one ormore lithography system components, semiconductor wafers may be moreprecisely and repeatedly etched according to tighter tolerances.

Further features and advantages of the invention as well as thestructure and operation of various embodiments of the present inventionare described in detail below with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings in which like reference numbers indicateidentical or functionally similar elements. Additionally, the left-mostdigit of a reference number identifies the drawing in which thereference number first appears.

FIG. 1 is a picture illustrating the image flip problem, in anembodiment of the present invention.

FIG. 2 is a diagram illustrating a typical lithographic system usingcatadioptric exposure optics, parallel reticle and wafer stages and amagnifying mirror.

FIG. 3 is a diagram illustrating a lithographic system using thecentrally obscured optical system design.

FIG. 4 is a diagram illustrating a lithographic system using theoff-axis design.

FIG. 5 is a diagram illustrating a lithographic system using orthogonalreticle and wafer stages, in an embodiment of the present invention.

FIG. 6 is a diagram illustrating the catadioptric exposure optics of alithographic system using orthogonal reticle and wafer stages, in anembodiment of the present invention.

FIG. 7 is a diagram illustrating the image path in a lithographic systemusing orthogonal reticle and wafer stages, in an embodiment of thepresent invention.

FIG. 8 is a chart illustrating the orientation of an image duringprocessing within the catadioptric exposure optics, in an embodiment ofthe present invention.

FIG. 9 is an illustration of a dual wafer stage, in an embodiment of thepresent invention.

FIG. 10 is an illustration of a dual isolation system, in an embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION Table of Contents

I. Overview

A. Definitions

B. General Considerations

II. System Orientation

III. Exposure Optics

A. Image Path

B. Projected Image

IV. Dual Wafer Stage

V. Dual Isolation System

VI. Conclusion

DETAILED DESCRIPTION OF THE INVENTION

I. Overview

The present invention relates to a lithography system and method usingcatadioptric exposure optics that projects high quality images withoutimage flip. The present invention allows for a more efficient and timelyproduction of semiconductors.

A. Definitions

The following definitions are provided for illustrative purposes only.Alternative definitions for the listed terms will be apparent to personsskilled in the relevant art(s) based on the discussion contained herein,and fall within the scope and spirit of embodiments of the invention.

The term “catadioptric” refers to the use of reflective and refractiveelements (i.e., mirrors and lenses).

B. General Considerations

The present invention is described in terms of the examples containedherein. This is for convenience only and is not intended to limit theapplication of the present invention. In fact, after reading thefollowing description, it will be apparent to one skilled in therelevant art(s) how to implement the following invention in alternativeembodiments.

II. System Orientation

FIG. 5 is a diagram illustrating a lithographic system 500, in anembodiment of the present invention. The figure shows a reticle stage502, a wafer stage 504 and catadioptric exposure optics 506. Duringoperation of system 500, an image (not shown) is associated with reticlestage 502. Subsequently, the image is projected into catadioptricexposure optics 506, which processes the image and projects the imageonto wafer stage 504. Alternatively, the image can be reflected intocatadioptric exposure optics 506. Heretofore, any reference to theprojection of the image from reticle stage 502 into catadioptricexposure optics 506 will be interchangeable with the reflection of theimage into the same.

In an embodiment of the present invention, reticle stage 502 isorthogonal to wafer stage 504. To illustrate this configuration, usingFIG. 5 as an example, reticle stage 502 is situated on a first planewhile wafer stage 504 is situated on a second plane, wherein the firstplane is orthogonal to the second plane. This feature allows for theimage orientation of the image projected onto wafer stage 504 to becongruent to the image orientation of the original image (i.e., theimage is not flipped). Image orientation is explained in greater detailbelow.

III. Exposure Optics

FIG. 6 is a diagram illustrating a more detailed view of a catadioptricexposure optics 600, in an embodiment of the present invention. FIG. 6shows entrance lenses 602, beam splitter 604, concave asphere 606 (i.e.,magnifying mirror) and exit lenses 610. FIG. 6 is shown for illustrativepurposes only and does not seek to limit the present invention to theillustrated configuration. The highly sophisticated catadioptricexposure optics 600 includes such components as may be necessary in, forexample, step-and-scan type lithographic tools. An example ofcatadioptric exposure optics is described in commonly-owned U.S. Pat.No. 5,537,260 to Williamson, entitled “Catadioptric Optical ReductionSystem with High Numerical Aperture.” The foregoing U.S. Patent ishereby incorporated by reference in its entirety.

Entrance lenses 602 are situated upon the entrance of catadioptricexposure optics 600. As an image enters catadioptric exposure optics600, lenses 602 magnify and/or align the image. In addition, entrancelenses 602, or any other component situated upon the entrance ofcatadioptric exposure optics 600, can perform any task known to one ofskill in the art.

Beam splitter 604 is a polarized mirror. Thus, light of the samepolarity as beam splitter 604 can pass through it, while light of adifferent polarity is reflected by it. It should also be noted that beamsplitter 604 is situated at a 45 degree angle from the incidence of theangle of an incoming image. Using FIG. 6 as an example, beam splitter604 is situated at a 45 degree angle from the horizontal plane. Thisfeature allows an incoming image to be reflected directly into concaveasphere 606, due to Snell's Law (i.e., the angle of incidence is equalto the angle of reflection).

Concave asphere 606 increases the magnitude of an incoming imagereflected by beam splitter 604. In addition, concave asphere 606reverses the polarity of light carrying an incoming image reflected bybeam splitter 604. Concave asphere 606 performs these tasks, as well asany other potential tasks, in a manner which is known to those skilledin the art of the present invention.

Exit lenses 610 are situated upon the exit of catadioptric exposureoptics 600. As an image exits catadioptric exposure optics 600, lenses610 magnify and/or align the image. In addition, exit lenses 610, or anyother component situated upon the exit of catadioptric exposure optics600, can perform any task known to one of skill in the art.

A. Image Path

FIG. 7 is a diagram illustrating the path taken by an image withinexample catadioptric exposure optics 700, in an embodiment of thepresent invention. In this embodiment, an image 702 enters catadioptricexposure optics 700 through a designated entrance. As image 702 enterscatadioptric exposure optics 700, lenses 602 magnify and/or align image702.

Subsequently, image 702 enters beam splitter 604. The light carryingimage 702 through the entrance of catadioptric exposure optics 700 is ofopposite polarity as beam splitter 604. Thus, image 702 is reflected bybeam splitter 604. Due to the orientation of beam splitter 604 (i.e.,its 45 degree angle), image 702 is reflected directly into concaveasphere 606.

Next, image 702 is reflected off of concave asphere 606. Concave asphere606 then increases the magnitude of image 702 and reverses the polarityof image 702. In addition, concave asphere 606, as known to one of skillin the art, flips the image around both axes. As a result, after beingreflected by concave asphere 606, the light carrying image 702 is of theequal polarity as beam splitter 604.

Since the light carrying image 702 is now of equal polarity as beamsplitter 604, image 702 passes through beam splitter 604. Then, image702 is projected toward the exit of catadioptric exposure optics 700. Indoing so, the image passes through exit lenses 610. As image 702 exitscatadioptric exposure optics 700, lenses 610 magnify and/or align image702. Subsequently, image 702 is projected onto wafer stage 504.

B. Projected Image

FIG. 8 is a chart 800 illustrating the orientation image 702 duringprocessing within the catadioptric exposure optics, in an embodiment ofthe present invention. It should be noted that a rotation of the imageof 180° is not a permanent problem, as this requires a simple rotationof the wafer 180° to correct. FIG. 8 shows how image 702 changes duringprocessing by catadioptric exposure optics 700, as described in FIG. 7above. The left column of chart 800 provides a description of theprocessing stage of image 702, as well as the viewing perspective. Inother words, the left column describes where in the process image 702 iscurrently located, and how image 702 should be viewed.

The right column of chart 800 shows a representation of image 702 fromthe defined viewing perspective and at the defined processing stage.

The first row of chart 800 shows that image 702 is originally an imageof the letter “F” if viewed from the perspective of a person standingbehind catadioptric exposure optics 700 and looking into the entrance.The image of the second row of chart 800 is basically the image of thefirst row, rotated. The image of the second row is significant becauseit represents how the wafer will be viewed.

As explained above, it can be seen that, using the lithographic systemand method of the present invention, an original image of the letter “F”will be projected as the image “” onto wafer stage 504. It can be shownthat the original image “F” is congruent to the projected image “”. Thisassertion becomes more clear when the projected image “” is rotated onehundred and eighty (180) degrees clockwise. After the rotation, theprojected image “” becomes identical to the original image “F.” Incontrast, an image that has undergone one image flip is not congruent tothe original image. This is because there are no number of rotations ofthe flipped image that will render the flipped image identical to theoriginal image.

Further, the lithographic system of the present invention does notposses the problems associated with alternative lithographic systemdesigns (as described above), such as the centrally obscured opticalsystem design (see FIG. 3) and the off-axis design (see FIG. 4). Onereason for this is because the lithographic system of the presentinvention does not utilize a configuration using a magnifying mirrorwith a small hole, through which the image passes. Thus, thelithographic system of the present invention does not exhibit obscuredareas.

Another reason why the lithographic system of the present invention doesnot posses the problems associated with alternative lithographic systemdesigns is because of the use of the magnifying mirror. The lithographicsystem of the present invention projects images directly (i.e,perpendicularly) into the magnifying mirror (i.e., the concave asphere).In addition, the lithographic system of the present invention projectsimages directly out of the magnifying mirror and directly onto anothersurface, such as the wafer stage. Thus, the lithographic system of thepresent invention does not exhibit perspective warping and relatedproblems.

IV. Dual Wafer Stage

In an embodiment of the present invention, a dual wafer stage is used tomake the manufacturing process more efficient. A dual wafer stageincludes the use of two, separate wafer stages operating in tandem, suchthat one wafer may be exposed while the other is loading. Thisembodiment of the present invention increases lithography toolthroughput while simultaneously increasing the volume of alignment datacollected through the use of two substrate stages. Each substrate stagehas associated load/unload and data collection stations. The load/unloadand data collection stations are located on either side of an exposurestation. The substrate stages are mounted on a common rail such that asa first stage moves away from the exposure station, a second stage canimmediately move in to take its place under the exposure apparatus.Through this arrangement, use of the exposure apparatus is maximized.Because wafer data collection and exposure steps occur in parallel inthe instant invention, the compromised wafer alignment strategiessometimes employed to increase throughput need not be used. In fact, theparallel nature of the instant invention allows for greater datacollection without a corresponding decrease in throughput.

In another embodiment of the present invention, the lithographyapparatus comprises an exposure station and a plurality of substratestages, each of the substrate stages having an associated datacollection station separate from a data collection station associatedwith other of the plurality of substrate stages. Each of the pluralityof substrate stages is movable from the associated data collectionstation to the exposure station.

During operation, each of the plurality of substrate stages isalternately moved from its associated data collection station to theexposure station such that data collection of a first of the pluralityof substrate stages can occur at the same time a second of the pluralityof substrate stages is undergoing exposure at the exposure station.

The lithography apparatus can further be characterized as includingfirst and second data collection cameras disposed over first and thirdpositions within the apparatus. The exposure apparatus being disposedover a second position within the lithography apparatus. The first andsecond substrate stages being movable from the first position to saidsecond position and from the third position to the second position,respectively.

FIG. 9 illustrates a dual wafer stage, in an embodiment of the presentinvention. Data collection and exposure structure 900 includes a firstwafer stage 910 and a second wafer stage 920. The first and second waferstages are depicted in the figures as having wafers 911 and 921 mountedthereon. Wafer stage 910 is mounted via sub-stages 912 and 913 to rail930. Sub-stage 913 is movably mounted to sub-stage 912 to permit stagemovement in a direction perpendicular to rail 930. Though not shown,substages 912 and 913 can include components of a linear brushless motorof the type known to those skilled in the art to effectuate thismovement. Motors 931 and 932 propel sub-stage 913 along the rail 930.Motors 931 and 932 can also be linear brushless motors of the type knownto those skilled in the art. Likewise, wafer stage 920 is mounted torail 930 via sub-stages 922 and 926. Motors 931 and 932 also propelsub-stage 926 along rail 930. As with sub-stages 912 and 913, anadditional motor components are included within sub-stages 922 and 926to effectuate stage movement in a direction perpendicular to rail 930.Furthermore, interferometers (not shown) are disposed within thestructure to accurately determine the location of wafer stages 910 and920 on rail 930 and along an axis perpendicular to 930. Theseinterferometers work together with a control system to control stagemovement.

Data collection and exposure structure 900 works together with first andsecond data collection cameras 940 and 950, respectively. These camerasare mounted to a structure separate from the data collection andexposure apparatus. These data collection cameras are of the type knownto those skilled in the art as being capable of data gathering forcalibration functions such as wafer alignment target mapping and waferflatness mapping. The first and second data collection cameras aremounted above regions referred to herein respectively as first andsecond data collection stations. The term data collection station ismeant to refer to a region along rail 930 where wafer data collectionoccurs during operation and is not meant to be limited to a singleparticular wafer stage location within the structure. The datacollection station associated with each data collection camera is largerin area than its associated wafer stage since each wafer stage moveswithin its associated data collection station during the data collectionprocess. Data collection cameras 940 and 950 communicate with a controlsystem.

Data collection and exposure structure 900 further works together withexposure apparatus 960. While exposure optics are used in the case ofphotolithography, a different type of exposure apparatus may be useddepending on the particular application. For example, x-ray, ion,electron, or photon lithographies each may require a different exposureapparatus, as is known to those skilled in the art. The particularexample of photolithography is discussed here for illustrative purposesonly. Exposure optics 960 are mounted to the same structure, separatefrom the data collection and exposure apparatus, to which datacollection cameras 940 and 950 are mounted, as discussed above. Exposureoptics are of the type known to those skilled in the art as beingcapable of lithographic exposure functions. These exposure optics caninclude, for example, components and functionality for use instep-and-scan type tools as well as step and repeat tools where the fullreticle field is exposed without scanning. Exposure optics 960 isdisposed above a region referred to herein as the exposure station. Theterm exposure station is meant to refer to a region along rail 930 wherewafer exposure occurs during operation and is not meant to be limited toa single particular wafer stage location within the structure. Theexposure station is larger in area than a single one of the wafer stagessince the wafer stage being exposed moves within the exposure stationduring the wafer exposure process. The exposure station is locatedbetween the first and second data collection stations.

The concept of a dual wafer stage is explained in more detail incommonly-owned U.S. patent application Ser. No. 09/449,630, nowabandoned to Roux et al, entitled “Dual Stage Lithography Apparatus andMethod,” filed Nov. 30, 1999. The foregoing U.S. Patent Application ishereby incorporated by reference in its entirety.

Referring to FIG. 5, a dual wafer stage, as described above, can beinterchanged with wafer stage 504. The combination of a dual wafer stagewith lithographic system 500 yields a lithographic system capable ofhigh throughput while using catadioptric exposure optics that produce ahigh quality image without image flip.

V. Dual Isolation System

In an embodiment of the present invention, a dual isolation system isused to make the manufacturing process more precise. A dual isolationsystem includes the isolation of the wafer stage and the reticle stage,such that both stages are protected from environmental motion. In oneaspect, an isolated base frame is supported by a non-isolated toolstructure. A wafer stage component is supported by the isolated baseframe. The wafer stage component provides a mount for attachment of asemiconductor wafer. A reticle stage component is supported by theisolated base frame. The reticle stage component provides a mount for areticle. An isolated bridge provides a mount for a projection optics.The isolated bridge is supported by the isolated base frame. Radiationfrom an illumination source passes through a reticle mounted at theprovided reticle mount to a surface of an attached semiconductor wafer.A pattern of a mounted reticle is transferred to a surface of anattached semiconductor wafer.

In another aspect, an isolated bridge provides a mount for a projectionoptics. The isolated bridge is supported by a non-isolated base frame. Awafer stage component is supported by the non-isolated base frame. Thewafer stage component provides a mount for attachment of a semiconductorwafer. A reticle stage component is supported by the non-isolated baseframe. The reticle stage component provides a mount for a reticle. Anisolated optical relay is supported by the non-isolated base frame. Theisolated optical relay includes at least one servo controlled framingblade. The one or more servo controlled framing blades are configuredsuch that radiation from an illumination source would be framed andimaged onto a reticle mounted at the provided reticle mount. Theradiation would pass through the reticle plane to a surface of anattached semiconductor wafer. A pattern of a mounted reticle would betransferred to an attached semiconductor wafer surface.

FIG. 10 illustrates a dual isolation system, in an embodiment of thepresent invention. Lithographic tool apparatus 1100 incorporates anisolation system to minimize motion in the structure supporting criticaloptical components. Lithographic tool apparatus 1100 includes anisolated bridge 1102, a projection optics 1104, a first, second, andthird pneumatic isolator 1106, 1108, and 1110, a non-isolated base frame1112, a first and second relative position sensor 1114 and 1116, afirst, second, third, and fourth actuator 1118, 1120, 1122, and 1124, awafer sub-stage 1126, a wafer precision stage 1128 with a bracket 1142,a focus back plate 1130, one or more flexured spacing rods 1132, areticle stage 1134, a linear motor 1136, a 1× relay 1138, and air bars1140. These elements of lithographic tool apparatus 1100 are more fullydescribed in the following text and subsections below.

The concept of a dual isolation system is explained in more detail incommonly-owned U.S. Pat. No. 6,538,720, to Galburt et al, entitled“Lithographic Tool with Dual Isolation System and Method for Configuringthe Same,” issued Mar. 25, 2003. The foregoing U.S. Patent Applicationis hereby incorporated by reference in its entirety.

Referring to FIG. 5, a dual isolation system, as described above, can beintegrated with wafer stage 504. The combination of a dual isolationsystem with lithographic system 500 yields a lithographic system capableof increased operational precision while using catadioptric exposureoptics that produce a high quality image without image flip.

VI. Conclusion

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. It will be apparent to persons skilled inthe relevant art(s) that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.Thus the present invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

What is claimed is:
 1. A lithography apparatus, comprising: a reticlestage that one of transmits or reflects an image; an exposure station; aplurality of wafer stages, each of said wafer stages having anassociated data collection station separate from a data collectionstation associated with other of said plurality of wafer stages, whereinsaid reticle stage is oriented substantially orthogonal to each of saidplurality of wafer stases; and a catadioptric exposure optics element,oriented between said reticle stage and one of said plurality of waferstages, that causes an even number of reflections of said image and thatprojects said image onto said one of said plurality of wafer stages in acongruent manner.
 2. The lithography apparatus of claim 1, wherein saidprojected image substantially lacks aberrations, including any one of:perspective warping; and obscured areas.
 3. The lithography apparatus ofclaim 1, wherein each of said plurality of wafer stages is movable fromsaid associated data collection station to said exposure station.
 4. Thelithography apparatus of claim 1, wherein during operation each of saidplurality of wafer stages is alternately moved from said associated datacollection station to said exposure station such that data collection ofa first of said plurality of wafer stages can occur at the same time asecond of said plurality of wafer stages is undergoing exposure at saidexposure station.
 5. The lithography apparatus of claim 1, furthercomprising: a first data collection camera disposed over a firstposition within the apparatus; an exposure apparatus disposed over asecond position within the apparatus; and a second data collectioncamera disposed over a third position within the apparatus, wherein saidplurality of wafer stases includes a first wafer stage movable from saidfirst position to said second position; and a second wafer stage movablefrom said third position to said second position.
 6. The lithographyapparatus of claim 5, further comprising a rail, said first and saidsecond wafer stages movably mounted to said rail.
 7. A lithographyapparatus comprising: a reticle stage that one of transmits or reflectsan image; a wafer stage, said reticle stage oriented substantiallyorthogonal to said wafer stage; a catadioptric exposure optics element,oriented between said reticle stage and said wafer stage, that causes aneven number of reflections of said image and that projects said imageonto said wafer stage in a congruent manner; and a dual isolation systemcomprising an isolated base frame supported by a non-isolated toolstructure; a wafer stage component to provide a mount for attachment ofa semiconductor wafer, supported by said isolated base frame; a reticlestage component to provide a mount for a reticle, supported by saidisolated base frame; and an isolated bridge to provide a mount for saidcatadioptric exposure optics element, supported by said isolated baseframe.
 8. A lithography method, comprising the steps of: providing areticle stage for transmitting or reflecting an image; providing anexposure station; providing a plurality of wafer stages for receivingthe image, each of said wafer stages having an associated datacollection station separate from a data collection station associatedwith other of said plurality of wafer stages; orienting said reticlestate substantially orthogonal to each of said plurality of waferstages; and orienting a catadioptric exposure optics element betweensaid reticle stage and said wafer stage to cause an even number ofreflections of said image and to project said image onto said waferstage in a congruent manner.
 9. The lithography method of claim 8,further comprising the step of projecting an image substantially lackingin aberrations, including any one of: perspective warping; and obscuredareas.
 10. The lithography method of claim 8, further comprising thestep of allowing each of said plurality of wafer stages to be movablefrom said associated data collection station to said exposure station.11. The lithography method of claim 8, further comprising the step ofalternately moving each of said plurality of wafer stages duringoperation from said associated data collection station to said exposurestation such that data collection of a first of said plurality of waferstages can occur at the same time a second of said plurality of waferstages is undergoing exposure at said exposure station.
 12. Thelithography method of claim 8, further comprising the steps of:providing a first data collection camera disposed over a first position;providing an exposure apparatus disposed over a second position; andproviding a second data collection camera disposed over a thirdposition, wherein said step of providing a plurality of wafer stasesincludes providing a first wafer stage movable from said first positionto said second position; and providing a second wafer stage movable formsaid third position to said second position.
 13. The lithography methodof claim 12, further comprising the step of providing a rail, said firstand said second wafer stages movably mounted to said rail.
 14. Alithography method comprising the steps of: providing a reticle stagefor transmitting or reflecting an image; providing a wafer stage forreceiving the image; orienting said reticle stage substantiallyorthogonal to said wafer stage; orienting a catadioptric exposure opticselement between said reticle stage and said wager stage to cause an evennumber of reflections of said image and to project said image onto saidwafer stage in congruent manner; providing an isolated base framesupported by a non-isolated tool structure; providing a wafer stagecomponent to provide a mount for attachment of a semiconductor wafer,supported by said isolated base frame; providing a reticle stagecomponent to provide a mount for a reticle, supported by said isolatedbase frame; and providing an isolated bridge to provide a mount for saidcatadioptric exposure optics element, supported by said isolated baseframe, wherein a dual isolation method is provided.